Molecules that contain two or more atoms capable of forming donor (i.e., coordinate) bonds to a single metal atom are termed chelating agents, or chelators, and the corresponding metal complexes are called chelates. The number of donor atoms present in a chelator is termed its denticity.
The chemical abbreviations used in this application are according to the Periodic Table.
The first anti-chelate antibody was described by Meares, et al., U.S. Pat. No. 4,722,892. Subsequent disclosures have described monoclonal antibodies raised against the cobalt (II) complex of ethylenediaminetetraacetic acid (EDTA) [Goodwin, et al., J. Nucl. Med., 29:226-34 (1988)], indium (III) complexes of diethylenetriaminepentaacetic acid (DTPA) [Gillette, et al., J. Immunol. Methods, 124:277-82 (1989); Le Doussal, et al., Cancer Res., 50:3445-52 (1990)], iron (III) and cobalt (II) complexes of meso-tetrakis(carboxyphenyl)porphyrin [Schwabacher, et al., J. Am. Chem. Soc., 111:2344-46 (1989)], N-methylmesoporphyrin IX [Cochran, et al., Science, 249:781-83 (1990)], the tin (IV) complex of meso-tetrakis(4-carboxyvinylphenyl)porphyrin [Keinan, et al., Pure Appl. Chem., 62:2013-19 (1990)] and the gallium (III) complex of HBED [Zoller, et al., J. Nucl. Med., 33:1366-72(1992)]. Blake et al., [J. Biol. Chem., 271:27677-85 (1996)] disclose a monoclonal antibody, 2A8165, raised against a benzyl-EDTA complex of cadmium (II). The 2A81G5 antibody binds to the cadmium (II) complex of EDTA with good affinity, but also binds to the mercury (II) complex of EDTA with slightly higher affinity and to the EDTA chelates of indium (III) and manganese (II) with affinities only 3-fold and 5-fold lower, respectively, than that for Cd-EDTA. U.S. Pat. Nos. 5,476,939 and 5,631,172 of Johnson describe certain chelators, chelates, labelled tracers, antibodies directed to the chelates, and immunoassays using the antibodies and tracers. In particular, U.S. Pat. No. 5,476,939 discloses chelators derived from pyridyl and isoquinolyl carbinolamines. In addition to these premeditated efforts, a polyclonal humoral anti-chelate response has been documented in some cancer patients receiving intravenous infusions of a monoclonal antibody conjugated to the yttrium (III) chelate of 1,4,7,10-tetraazacyclododecance-N, N',N"-tetraacetic acid (DOTA), a macrocyclic polyaminopolycarboxylate chelator [Kosmas, et al., Cancer Res., 52:904-11 (1992)].
Chakrabarti et al., [Anal. Biochem., 217:70-75 (1994)] disclose the use of an indium-specific monoclonal antibody in an enzyme linked immunosorbent assay (ELISA) for indium (III). Wagner et al., W09010709, disclose monoclonal antibodies raised against mercury (II) and lead (II) complexes of the naturally occurring chelator glutathione and their use in heterogeneous immunoassays for these metal ions.
Quay, U.S. Pat. No. 4,687,659, discloses reaction of the cyclic dianhydride of diethylenetriaminepentaacetic acid (DTPA) with alkyl amines to give diethylenetriamine-N, N', N"-triacetic acid (DTTA) diaminde derivatives used to prepare magnetic resonance image (MRI) contrast agents. Franklin et al., [Inorg. Chem., 33:5794 (1994)] disclose reaction of the cyclic dianhydride of DTPA with a diamine to give a cyclic diamide of DTTA. Li et al., [Bioconjugate Chem., 8:127-132 (1997)] disclose the step-wise reaction of the cyclic dianhydride of DTPA with various alkyl and aryl amines to give luminescent bifunctional lanthanide chelates.
Fluorescent polarization techniques are based on the principle that a fluorescent labelled compound when excited by linearly polarized light will emit fluorescence having a degree of polarization inversely related to its rate of rotation. Therefore, when a fluorescent labelled tracer-antibody complex is excited with linearly polarized light, the emitted light remains highly polarized because the fluorophore is constrained from rotating between the time light is absorbed and emitted. When a "free" tracer compound (i.e., unbound to an antibody) is excited by linearly polarized light, its rotation is much faster than the corresponding tracer-antibody conjugate and the molecules are more randomly oriented, therefore, the emitted light is depolarized. Thus, fluorescent polarization provides a quantitative means for measuring the amount of tracer-antibody conjugate produced in a competitive binding immunoassay.
The fluorescent polarization technique was first applied to antibody-antigen interaction by Dandliker et al. [Immunochem., 7:799-828 (1970); and Immunol. Chem., 10:219-227 (1973)]. Examples of commercially available fluorescence polarization instruments are: IMx.RTM. and Tdx.RTM. analyzers (from Abbott Laboratories, Abbott Park, Ill.) and analyzers from Panvera, Inc., Madison, Wis. None of these are specifically directed to the detection or quantification of metal ions.